Process for producing 1,3-dialkyl-2-imidazolidinone compound

ABSTRACT

There is provided a process for preparing a 1,3-dialkyl-2-imidazolidinone by using an alkylene oxide as a first component, using at least one of (A) carbon dioxide and a monoalkylamine; (B) a carbon dioxide compound of the monoalkylamine; and (C) an 1,3-dialkylurea, reacting the first and second components by heating at 50° C. or higher to give 1,3-dialkyl-2-imidazolidinone, characterized in that the total molar amount of a molar feed amount of the monoalkylamine included in the component (A), a molar feed amount of the monoalkylamine part of the carbon dioxide compound of monoalkylamine, component (B), and the double of a molar feed amount of the 1,3-dialkylurea, component (C), is at least three folds of a molar feed amount of the alkylene oxide. 
     The preparation process of this invention uses an industrially readily available alkylene oxide as a starting material and can be suitably conducted with a higher yield in an industrial scale.

TECHNICAL FIELD

This invention relates to a process for preparing1,3-dialkyl-2-imidazolidinones.

1,3-Dialkyl-2-imidazolidinones have been widely used as an aprotic polarsolvent. For example, they are useful as a solvent for a resin such aspolyamides, polyesters, polyvinyl chlorides and phenol resins; a solventfor a variety of organic synthetic reactions; or an extraction solventfor extracting an aromatic hydrocarbon from a mixture of hydrocarbons.Among those, 1,3-dimethyl-2-imidazolidinone (hereinafter, sometimesreferred to as “DMI”) is particularly useful because it exhibitsparticularly higher resistance to a strong alkali and thus is littledecomposed even when heated with an alkali-metal hydroxide solution. Itis, therefore, also preferred as a solvent for dehalogenation of anaromatic organohalide.

BACKGROUND ART

Various processes using N,N′-dimethylethylenediamine as a startingmaterial have been proposed for preparing1,3-dialkyl-2-imidazolidinones; for example, reactingN,N′-dimethylethylenediamine with trichloromethyl chloroformate (JP-A53-73561); reacting N,N′-dimethylethylenediamine with carbon dioxide(JP-A 57-175170); reacting N,N′-dimethylethylenediamine with phosgene inthe presence of water and a dehydrochlorinating agent (JP-A 61-109772and JP-A 61-172862); and reacting N,N′-dialkylethylenediamine with ureain a polar solvent (JP-A 7-252230). A known process for preparingN,N′-dialkylethylenediamines as a starting material such asN,N′-dimethylethylenediamine described above is based on ethylenedichloride and monomethylamine as described in JP-A 57-120570. Theprocess, however, produces a large amount of salt contaminated withorganic compounds as a byproduct, which may cause a difficult issue ofdisposal. J. Organometallic Chem., 407, 97 (1991) has described aprocess where ethylene glycol is reacted with monomethylamine in thepresence of a homogeneous catalyst comprising ruthenium andtriphenylphosphine. Recovery and recycle of a homogeneous noble metalcatalyst is, however, industrially difficult. Therefore, a process usingN,N′-dialkylethylenediamine as a starting material is not ideal forpreparing 1,3-dialkyl-2-imidazolidinone.

In addition, there have been proposed reduction of 2-imidazolidinone andformaldehyde in the presence of a hydrogenation catalyst (JP-A60-243071) and catalytic reduction of N,N′-hydroxymethylimidazolidinonedialkyl ether (JP-B 60-3299). These processes, however, employ astarting material derived from ethylenediamine. which may also cause theproblem described above, and are impractically longer processes.

Alternative processes have been disclosed, including reacting anN-alkylmonoethanolamine and an alkylamine such as monomethylamine withcarbon dioxide, an alkylamine alkylcarbamate or 1,3-dialkylurea (JP-A57-98268); reacting ethylene glycol, carbon dioxide and monomethylamineat an elevated temperature under a higher pressure (JP-A 59-155364); andreacting alkylene carbonate with monoalkylamine (JP-A10-502917). Theseprocesses are one-step processes, and an N-alkylmonoethanolamine,ethylene glycol and an alkylene carbonate as starting materials can bereadily prepared from an alkylene oxide. These processes are, therefore,noteworthy. These processes have a problem of production ofN-alkyldiethanolamines as byproducts during preparing anN-alkylmonoethanolamine from ethylene oxide. JP-A 10-330366 hasdisclosed a process for preparing DMI by a one-pot reaction fromethylene oxide, which has a problems of a lower yield.

In these processes, a monoalkylamine as a starting material isdisproportionated during a reaction to give disproportionationbyproducts, i.e., ammonia, a dialkylamine and/or a trialkylamine. JP-B1-15503 has disclosed a process where ethylene glycol is used as astarting material and unreacted materials containing a monoalkylamine iscirculated and recycled in a reactor. In this process, ammonia as abyproduct is also circulated so that repeated circulation may increaseammonia, leading to increase of byproducts such as1-alkyl-2-imidazolidinones and reduction in an yield of desired1,3-dialkyl-2-imidazolidinones. Thus, this process has not beenindustrially available.

DISCLOSURE OF THE INVENTION

An objective of this invention is to provide a process for preparing1,3-dialkyl-2-imidazolidinones using an industrially readily availablealkylene oxide as a starting material with an improved yield which canbe suitably practicable in an industrial scale. Another objective ofthis invention is to provide a process for highly effectively preparing1,3-dialkyl-2-imidazolidinones by effectively separating or processingbyproducts such as N-alkyldiethanolamines, ammonia, dialkylamines,trialkylamines, 1-alkyl-2-imidazolidinones and 1,3-dialkylureas.

The inventors have conducted intense investigation for solving the aboveproblems and have found that these problems can be solved by a processfor preparing 1,3-dialkyl-2-imidazolidinones by heating a firstcomponent consisting of an alkylene oxide and a second componentconsisting of at least one of (A) carbon dioxide and a monoalkylamine,(B) a carbon dioxide compound of a monoalkylamine and (C) a1,3-dialkylurea at 50° C. or higher, wherein the second component ischarged such that the total of a molar amount of the chargedmonoalkylamine in the component (A), a molar amount of themonoalkylamine part in the charged carbon dioxide compound ofmonoalkylamine, component (B), and the double of a molar amount of thecharged 1,3-dialkylurea, component (C), is at least three folds of amolar amount of the charged alkylene oxide, achieving this invention.

This invention provides a process for preparing a1,3-dialkyl-2-imidazolidinone by using an alkylene oxide represented byformula (1) as a first component:

-   -   wherein in the formula (1), R¹ represents hydrogen or alkyl        group having 1 to 6 carbon atoms,    -   using at least one selected from the group consisting of the        following components (A), (B) and (C) as a second component:    -   component (A): carbon dioxide and a monoalkylamine represented        by formula (2):        R²NH₂  (2)    -   wherein in the formula (2), R²represents alkyl group having 1 to        6 carbon atoms;    -   component (B): a carbon dioxide compound of the monoalkylamine        represented by formula (2); and    -   component (C): an 1,3-dialkylurea represented by formula (3):        R²NHCONHR²  (3)    -   wherein in the formula (3), R² is as defined above,    -   and reacting said first component with said second component by        heating those components at 50° C. or higher to give        1,3-dialkyl-2-imidazolidinone represented by formula (4):    -   wherein in the formula (4), R¹ and R² are as defined above,    -   characterized in that the total molar amount of a molar feed        amount of the monoalkylamine included in the component (A), a        molar feed amount of the monoalkylamine part of the carbon        dioxide compound of monoalkylamine, said compound being        component (B), and the double of a molar feed amount of the        1,3-dialkylurea, said 1,3-dialkylurea being component (C), is at        least three folds of a molar feed amount of said alkylene oxide.

The reaction is preferably conducted under a pressure of 4 MPa orhigher.

It is also preferable that the total molar amount of a molar feed amountof the carbon dioxide included in the component (A), a molar feed amountof the carbon dioxide part of the carbon dioxide compound ofmonoalkylamine, said compound being the component (B) and a molar feedamount of the 1,3-dialkylurea, said 1,3-dialkylurea being the component(C), is at least one and half folds of a molar feed amount of saidalkylene oxide.

It is also preferable that R¹ is hydrogen atom; R² represents methyl;and the 1,3-dialkyl-2-imidazolidinone prepared is1,3-dimethyl-2-imidazolidinone.

In this process, it is also preferable that ethylene oxide is used assaid first component and at least one selected from the group consistingof the following components (D), (E) and (F) is used as said secondcomponent:

-   -   component (D): carbon dioxide and monomethylamine;    -   component (E): a carbon dioxide compound of monomethylamine; and    -   component (F): 1,3-dimethylurea, the process comprises:    -   (1) a 1,3-dimethyl-2-imidazolidinone preparation step of        preparing 1,3-dimethyl-2-imidazolidinone by heating said first        component and said second component at 50° C. or higher, and the        process further comprises:    -   (2) a first separation step of separating the reaction mixture        obtained in the 1,3-dimethyl-2-imidazolidinone preparation step        into    -   a first fraction containing monomethylamine, carbon dioxide and        a carbon dioxide compound of monomethylamine as main components,        and also containing water; and    -   a second fraction containing 1,3-dimethyl-2-imidazolidinone and        high-boiling compounds with a higher boiling point than that of        1,3-dimethyl-2-imidazolidinone as main components, and also        containing water;    -   (3) a second separation step of separating at least part of the        second fraction in the first separation step into    -   a first fraction containing water and low-boiling amines with a        boiling point higher than that of water and lower than that of        1,3-dimethyl-2-imidazolidinone as main components; and    -   a second fraction containing 1,3-dimethyl-2-imidazolidinone and        said high-boiling compounds as main components;    -   (4) a third separation step of separating the second fraction in        the second separation step into    -   a first fraction containing 1,3-dimethyl-2-imidazolidinone as a        main component; and    -   a second fraction containing said high-boiling compounds as main        components; and    -   (5) a fourth separation step of separating the first fraction in        the first separation step into    -   a first fraction containing ammonia, dimethylamine,        trimethylamine, a carbon dioxide compound of ammonia, a carbon        dioxide compound of dimethylamine and a carbon dioxide compound        of trimethylamine as main components, and also containing water;        and    -   a second fraction containing monomethylamine and a carbon        dioxide compound of monomethylamine as main components, and also        containing water,    -   where at least part of the second fraction in the fourth        separation step is supplied in the        1,3-dimethyl-2-imidazolidinone preparation step.

Furthermore, the above 1,3-dimethyl-2-imidazolidinone preparation stepmay be carried out by:

-   -   (6) a first reaction step of heating ethylene oxide and at least        one selected from the group consisting of the components        (D), (E) and (F) at 50° C. or higher to prepare        N-methyldiethanolamine and 2-(methylamino)ethanol; and    -   (7) a second reaction step of heating N-methyldiethanolamine and        2-(methylamino)ethanol prepared in the first reaction step with        at least one selected from the group consisting of the        components (D), (E) and (F) at 100° C. or higher to prepare        1,3-dimethyl-2-imidazolidinone, and    -   the second fraction in the fourth separation step may be        supplied in said first reaction step and/or said second reaction        step.

In the fourth separation step, at least part of the first fraction inthe first separation step may be contacted with carbon dioxide, heatedat 50° C. or higher, and separated by vapor-liquid separation to removethe first fraction in the fourth separation step into the gaseous phaseand obtain the second fraction in the fourth separation step from theliquid phase.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing an embodiment of a preparation processaccording to this invention.

FIG. 2 is a block diagram showing another embodiment of a preparationprocess according to this invention.

FIG. 3 is a block diagram showing another embodiment of a preparationprocess according to this invention.

FIG. 4 is a block diagram showing another embodiment of a preparationprocess according to this invention.

In these drawings, symbols represent the followings: 1: the1,3-dimethyl-2-imidazolidinone preparation step; 2: the first separationstep; 3: the second separation step; 4: the third separation step; 5:the fourth separation step; 6: the first reaction step; 7: the secondreaction step; 8: a seventh separation step; 9: a hydrolysis step; 10:an absorption step; 11: a fifth separation step; 12: a rectificationstep; 13: a sixth separation step.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, this invention will be described in detail.

This invention provides a process for preparing a1,3-dialkyl-2-imidazolidinone.

According to the process of this invention, the1,3-dialkyl-2-imidazolidinone is prepared by reacting the firstcomponent consisting of an alkylene oxide represented by the formula(1); and the second component consisting of at least one selected fromthe group consisting of:

-   -   component (A): carbon dioxide and a monoalkylamine represented        by the formula (2);    -   component (B): a carbon dioxide compound of the monoalkylamine        represented by the formula (2);    -   component (C): a 1,3-dialkylurea represented by the formula (3),        by heating those components at 50° C. or higher.

An alkylene oxide used as a starting material in the process of thisinvention is an alkylene oxide in which a straight or circular alkylgroup represented by R¹ has 1 to 6 carbon atoms, including, for example,ethylene oxide, propylene oxide, ethyloxirane, propyloxirane,(1-methylethyl)oxirane, cyclopropyloxirane, (1,1-dimethylethyl)oxirane,n-butyloxirane, (2-methylpropyl)oxirane, (1-methylpropyl)oxirane,(1-methylcyclopropyl)oxirane, (1,2-dimethylpropyl)oxirane,n-pentyloxirane, (2-methylbutyl)oxirane, (1-ethylpropyl)oxirane,(3-methylbutyl)oxirane, (1-methylbutyl)oxirane,(2,2-dimethylpropyl)oxirane, cyclopentyloxirane,(3,3-dimethylbutyl)oxirane, (1,1-dimethylbutyl)oxirane,(1-methylpentyl)oxirane, n-hexyloxirane, cyclopentylmethyloxirane andcyclohexyloxirane. Among these, ethylene oxide or propylene oxide ispreferable and ethylene oxide is more preferable because a1,3-dialkyl-2-imidazolidinone or 1,3-dialkylpropyleneurea as a producthas a variety of applications.

A monoalkylamine represented by the formula(2) which is one of thesecond component in this invention, is a monoalkylamine in which astraight or circular alkyl group represented by R² has 1 to 6 carbonatoms, including, for example, monomethylamine, monoethylamine,mono(n-propyl)amine, mono (iso-propyl) amine, mono (n-butyl) amine, mono(sec-butyl) amine, mono(iso-butyl) amine, mono (tert-butyl) amine, mono(n-amyl) amine, mono(1-methylbutyl)amine, mono(2-methylbutyl)amine, mono(iso-amyl) amine, mono (tert-amyl) amine, mono(neo-pentyl)amine, mono(1,2-dimethylpropyl) amine, mono(1-ethylpropyl)amine, mono (n-hexyl)amine and monocyclohexylamine. Among these, monomethylamine ormonoethylamine is preferable and monomethylamine is more preferablebecause 1,3-dimethyl-2-imidazolidinones or1,3-diethyl-2-imidazolidinones have a variety of applications.

A carbon dioxide compound of monoalkylamine, which is one of the secondcomponent in the process of this invention, includes, for example,carbonates, hydrogencarbonates and alkyl carbamates of monoalkylamine.

The carbon dioxide compound of monoalkylamine may be used as a solid ora solution such as an aqueous solution. Alternatively, components whichgenerate the carbon dioxide compound in the reaction system can be usedin combination.

1,3-Dialkylurea represented by the formula (3) which is one of thesecond component in the process of this invention, is 1,3-dialkylurea inwhich an alkyl group represented by R² has 1 to 6 carbon atoms,including, for example, 1,3-dimethylurea, 1,3-diethylurea,1,3-di(n-propyl)urea, 1,3-di(iso-propyl)urea, 1,3-di(n-butyl)urea,1,3-di(sec-butyl)urea, 1,3-di(iso-butyl)urea, 1,3-di(tert-butyl)urea,1,3-di(n-amyl)urea, 1,3-di(1-methylbutyl)urea,1,3-di(2-methylbutyl)urea, 1,3-di(iso-amyl)urea, 1,3-di(tert-amyl)urea,1,3-di(neo-pentyl)urea, 1,3-di(1,2-dimethylpropyl)urea,1,3-di(1-ethylpropyl)urea, 1,3-di(n-hexyl)urea and 1,3-dicyclohexylurea.Among these, 1,3-dimethylurea or 1,3-diethylurea is preferable and1,3-dimethylurea is more preferable because a1,3-dialkyl-2-imidazolidinone or 1,3-dialkylpropyleneurea as a producthas a variety of applications.

The 1,3-dialkylurea may be used as is commercially available or as asolution such as an aqueous solution. Alternatively, components whichgenerate the 1,3-dialkylurea in the reaction system may be used incombination.

The amount of the second component supplied for the reaction in theprocess of this invention is determined such that the total molar amountof the following i) to iii) included in the second component recoveredand recycled and in the second component newly supplied to a reactor ispreferably at least three folds, more preferably 3 to 40 folds bothinclusive of the molar amount of the alkylene oxide:

-   -   i) the molar amount of the monoalkylamine;    -   ii) the molar amount of the monoalkylamine part in the carbon        dioxide compound of the monoalkylamine; and    -   iii) the double of the molar amount of 1,3-dialkylurea.

The reaction can be conducted under the conditions departing from theabove range, but the total molar amount of less than three folds maylead to reduction in an yield of the 1,3-dialkyl-2-imidazolidinone. Thetotal molar amount of more than 40 folds may be disadvantageous becauseof reduction in a volumetric efficiency of a reactor, and increase in acost for recovery of the unreacted monoalkylamine, carbon dioxidecompound of the monoalkylamine and 1,3-dialkylurea. Without recoveringand recycling, it is sufficient to consider only the second componentnewly supplied into the reactor.

Since DMI as a product has a variety of applications as a solvent, it ismost preferable to use ethylene oxide as an alkylene oxide,monomethylamine as a monoalkylamine, a carbon dioxide compound ofmonomethylamine as a carbon dioxide compound of monoalkylamine, and1,3-dimethylurea as a 1,3-dialkylurea.

In a reaction in the process of this invention, a reaction system can bereplaced or pressurized with a gas.

In terms of a pressure, a pressure at a reaction temperature ispreferably 4 MPa or higher. Although the reaction may be conducted at apressure of less than 4 MPa, it may be disadvantageous because oftendency to reduction in a production efficiency of a1,3-dialkyl-2-imidazolidinone.

As a gas for replacement or pressurization as described above, carbondioxide is preferable because it can be also used as the secondcomponent, but another gas including an inert gas such as nitrogen andargon can be appropriately used. Using carbon dioxide results inimprovement in an yield of a 1,3-dialkyl-2-imidazolidinone. Carbondioxide may be used as gaseous, liquid, solid or supercritical carbondioxide. The amount of carbon dioxide supplied in this reaction isdetermined such that the total molar amount of carbon dioxide used fordisplacement or pressurization and the following iv) to vi) included inthe second component recovered and recycled and in the second componentnewly supplied is preferably at least one and half folds, morepreferably 4 to 100 folds both inclusive of the molar amount of thealkylene oxide supplied:

-   -   iv) the molar amount of carbon dioxide;    -   v) the molar amount of carbon dioxide part in the carbon dioxide        compound of alkylamine; and    -   vi) the molar amount of 1,3-dialkylurea.

The total molar amount of less than one and half folds isdisadvantageous because of tendency to reduction in a productionefficiency for the 1,3-dialkyl-2-imidazolidinone, while the total molaramount of more than 100 folds may be disadvantageous because of tendencyto reduction in a volumetric efficiency of the reactor.

A reaction in the process of this invention is conducted at 50° C. orhigher, preferably 50 to 300° C. both inclusive. A temperature of lowerthan 50° C. may be disadvantageous because of tendency to reduction in aproduction efficiency for the 1,3-dialkyl-2-imidazolidinone, while atemperature of higher than 300° C. may be disadvantageous because oftendency to increase in byproducts.

A reaction time depends on factors such as the amounts of startingmaterials and a reaction temperature; preferably 200 hours or less, morepreferably 0.01 to 100 hours both inclusive, further preferably 0.1 to50 hours both inclusive. A time of less than 0.01 hours may bedisadvantageous because of tendency to reduction in an yield of a1,3-dialkyl-2-imidazolidinone, while a time of more than 200 hours maybe disadvantageous because of tendency to reduction in a volumetricreaction efficiency.

A reaction in the process of this invention may be conducted neat orsometimes using a solvent. Any solvent which is inert to reactionsubstrates under the reaction condition may be used; preferably, water,hydrocarbons, ethers, amides, circular ureas and supercritical carbondioxide. Among these, water or a 1,3-dialkyl-2-imidazolidinone which isidentical to the product is more preferable because it can eliminate anadditional step of recovering a solvent because it is a reactionproduct.

These solvents may be used alone or in combination of two or more.Depending on a solvent used, the reaction may be conducted in amultiphase system of two or more phases.

The solvent may be suitably used in an amount sufficient to dissolve apart of at least one of the starting materials used. The amount ispreferably 100 parts by weight or less, more preferably 50 parts byweight or less to one part by weight of an alkylene oxide as a startingmaterial. An amount of more than 100 parts by weight is disadvantageousbecause of tendency to reduction in a volumetric efficiency.

In the process of this invention, a catalyst or additive may be used forfurther improving an yield or reaction rate.

A reactor used for a reaction in the process of this invention may bemade of an appropriate known material, and a reactor whose inner wall isat least partly made of the following material (I) is preferable becauseit may provide a 1,3-dialkyl-2-imidazolidinone with a higher yield:

-   -   (I) a metal and/or its oxide containing at least one selected        from the group consisting of titanium and zirconium.

Examples of such a reactor include those totally made of a metalcontaining titanium or zirconium; those whose inner wall is at leastpartly coated with a metal or its oxide containing titanium orzirconium. Examples of a metal containing titanium or zirconium includeindustrial pure titanium in JIS Groups 1 to 4; anticorrosion titaniumalloys such as Ti-0.15Pd, Ti-5Ta and Ti-0.3Mo-0.8Ni; α-type titaniumalloys such as Ti-2.5Sn, Ti-5Al-2.5Sn, Ti-5Al-2.5Sn(ELI), Ti-2.5Cu,Ti-2O-1N-5Fe, Ti-5Ni-0.5Ru, Ti-0.5Pd-3Co andTi-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si; near α-type titanium alloys such asTi-8Al-1Mo-1V, Ti-2.25Al-11Sn-5Zr-1Mo-0.2Si, Ti-6Al-2Sn-4Zr-2Mo,Ti-5Al-5Sn-2Zr-2Mo-0.25Sn, Ti-6Al-2Nb-1Ta-0.8Mo, Ti-6Al-5Zr-0.5Mo-0.2Siand Ti-4.5Al-3V-2Fe-2Mo; α+β-type titanium alloys such asTi-5Al-2Cr-1Fe, Ti-5Al-5Sn-5Zr-2Cr-1Fe, Ti-4Al-4Mn, Ti-3Al-2.5V,Ti-6Al-4V, Ti-6Al-4V(ELI), Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo,Ti-7Al-4Mo, Ti-5Al-2Zr-4Mo-4Cr, Ti-6Al-1.7Fe-0.1Si, Ti-6.4Al-1.2Fe,Ti-15Zr-4Nb-2Ta-2Pd, Ti-6Al-7Nb and Ti-8Mn; β-type titanium alloys suchas Ti-13V-11Cr-3Al, Ti-15Mo-5Zr, Ti-15Mo-0.2Pd, Ti-15V-3Cr-3Sn-3Al,Ti-20V-4Al-1Sn, Ti-22V-4Al and Ti-16V-4Sn-3Al-3Nb; near β-type titaniumalloys such as Ti-10V-2Fe-3Al and Ti-9.5V-2.5Mo-3Al; zirconium alloyssuch as zircaloy-2, zircaloy-4, Zr-2.5Nb and ozenite. Among thesemetals, titanium-containing metals are preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

In the process of this invention, an alkylene oxide and a monoalkylamineare reacted to give a 1,3-dialkyl-2-imidazolidinone via correspondingN-alkylmonoethanolamine and N-alkyldiethanolamine as intermediates.According to the process of this invention, a1,3-dialkyl-2-imidazolidinone can be, therefore, prepared by forming anN-alkylmonoethanolamine and N-alkyldiethanolamine at 50° C. or higherand then reacting these products at a further higher temperature. Insuch a case, the 1,3-dialkyl-2-imidazolidinone may be formed not onlyfrom the N-alkylmonoethanolamine but also from theN-alkyldiethanolamine. Thus, it is not necessary to separate these.

Any style of the process of this invention may be employed as long asstarting materials used can be effectively mixed and contacted withother material. Any of batch, semi-batch and continuous flow systems maybe employed; for example, charging all materials together in a reactor,continuous or intermittent feeding of at least one material into theother materials, or continuously or intermittently feeding allmaterials. Alternatively, after mixing the first component and a part ofthe second component, then the mixture may be fed into a reactor. Insuch a case, a reaction may proceed in a feed line, and anN-alkylmonoethanolamine and/or an N-alkyldiethanolamine may be formed inthe line.

In the process of this invention, a product solution may be, ifnecessary, treated as usual, for example, by distillation orcrystallization to provide a desired 1,3-dialkyl-2-imidazolidinone.

When a 1,3-dialkyl-2-imidazolidinone prepared by the process of thisinvention is DMI, it is preferably prepared according to a process flowshown in FIG. 1 or 2. FIGS. 3 and 4 show the embodiments in FIGS. 1 and2 with additional steps for further improving a production efficiency orpurity for DMI.

This invention will be described with reference to FIGS. 3 and 4.

As shown in FIG. 3, in 1,3-dimethyl-2-imidazolidinone preparation step(1), ethylene oxide, monomethylamine as one compound of the component(D) and carbon dioxide as another compound of the component (D) are fedto the 1,3-dimethyl-2-imidazolidinone preparation step via lines L1, L2and L3, respectively. The components (E) and/or (F) may be used in placeof or in addition to the component (D). In such a case, a carbon dioxidecompound of monomethylamine as the component (E) is fed to the1,3-dimethyl-2-imidazolidinone preparation step via line 52, while1,3-dimethylurea as the component (F) is fed via line 53. Ethyleneoxide, monomethylamine, carbon dioxide, the carbon dioxide compounds ofmonomethylamine and 1,3-dimethylurea may be fed by mixing at least twoof these in line L5 before introducing to the preparation step (1) or bydirectly introducing into a reactor without line L5. When employingmixing in line L5, line L5 may be heated for promoting a reaction in theline.

In these figures, EO represents ethylene oxide; mMA representsmonomethylamine; mMA-CO2 represents a carbon dioxide compound ofmonomethylamine; and DMU represents 1,3-dimethylurea.

In the 1,3-dimethyl-2-imidazolidinone preparation step, the amount ofthe second component supplied to the reaction is determined such thatthe total of the following i′) to iii′) is preferably at least threefolds, more preferably 3 to 40 folds both inclusive of the molar amountof ethylene oxide supplied. This molar ratio of less than 3 folds may bedisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while that of more than 40 folds may bedisadvantageous because of increase in a cost for recovering unreactedmonomethylamine, the carbon dioxide compound of monomethylamine and1,3-dimethylurea:

-   -   i′) the total of the molar amount of monomethylamine recovered        and recycled and the molar amount of monomethylamine newly        supplied;    -   ii′) the total of the molar amount of monomethylamine part in        the carbon dioxide compound of monomethylamine recovered and        recycled and the molar amount of monomethylamine part in the        carbon dioxide compound of monomethylamine newly supplied; and    -   iii′) the total of the double of the molar amount of        1,3-dimethylurea recovered and recycled and the double of the        molar amount of 1,3-dimethylurea newly supplied.

Carbon dioxide used in the 1,3-dimethyl-2-imidazolidinone preparationstep may be used as gaseous, liquid, solid or supercritical carbondioxide. Carbon dioxide discharged from lines L20 and L22 may berecovered for recycling.

The amount of the second component supplied for this reaction isdetermined such that the total of the following iv′) to vi′) ispreferably at least one and half folds, more preferably 4 to 100 foldsboth inclusive of the molar amount of ethylene oxide supplied. Thismolar ratio of less than one and half folds is disadvantageous becauseof tendency to reduction in a production efficiency for the1,3-dialkyl-2-imidazolidinone, while the molar ratio of more than 100folds may be disadvantageous because of tendency to reduction in avolumetric efficiency of the reactor:

-   -   iv′) the total of the molar amount of carbon dioxide part in the        carbon dioxide compound of monomethylamine recovered and        recycled and the molar amount of carbon dioxide part in the        carbon dioxide compound of monomethylamine newly supplied;    -   v′) the total of the molar amount of 1,3-dimethylurea recovered        and recycled and the molar amount of 1,3-dimethylurea newly        supplied; and    -   vi′) the total of the molar amount of carbon dioxide recovered        and recycled and the molar amount of carbon dioxide newly        supplied.

The reaction in the 1,3-dimethyl-2-imidazolidinone preparation step isconducted at 50° C. or higher, preferably 50 to 300° C. both inclusive.A temperature of lower than 50° C. leads to reduction in a productionefficiency for DMI. A temperature of higher than 300° C. may bedisadvantageous because of tendency to increase in byproducts.

A pressure depends on factors such as a temperature and startingmaterials; preferably 4 MPa to 30 MPa both inclusive. A pressure of lessthan 4 MPa may be disadvantageous because of tendency to reduction in aproduction efficiency for 1,3-dimethyl-2-imidazolidinone, while apressure of more than 30 MPa may be disadvantageous because of increasein a production cost of a reactor.

A reaction time depends on factors such as the amounts of startingmaterials and a reaction temperature; preferably 200 hours or less, morepreferably 0.01 to 100 hours both inclusive, more preferably 0.1 to 50hours both inclusive. A time of less than 0.01 hours may bedisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while a time of more than 200 hours maybe disadvantageous because of tendency to reduction in a volumetricreaction efficiency.

In the 1,3-dimethyl-2-imidazolidinone preparation step, the reaction maybe conducted in the presence of water, which is introduced via lines L4and L5. The amount of water supplied to the reaction is determined suchthat the amount of water recovered and recycled and water newly suppliedis preferably 100 parts by weight or less, more preferably 50 parts byweight or less to one part by weight of ethylene oxide supplied. Theamount of more than 100 parts by weight is disadvantageous because ofreduction in a volumetric efficiency of the reactor.

The 1,3-dimethyl-2-imidazolidinone preparation step may be carried outby two steps, as shown in FIG. 4, i.e., a first reaction step (6) forpreparing 2-(methylamino)ethanol and N-methyldiethanolamine; and asecond reaction step (7) for preparing DMI from 2-(methylamino)ethanoland N-methyldiethanolamine prepared in the first reaction step (6).

In this case, to the first reaction step are fed ethylene oxide vialines L43, monomethylamine as one compound in the component (D) via lineL40 and carbon dioxide as another compound in the component (D) via lineL41. Alternatively, the component (E) and/or (F) may be used in place ofor in addition to the component (D). In such a case, the carbon dioxidecompound of monomethylamine as the component (E) is fed via line L54 tothe first reaction step while 1,3-dimethylurea as the component (F) isfed via line L55. Ethylene oxide, monomethylamine, carbon dioxide, thecarbon dioxide compound of monomethylamine and 1,3-dimethylurea may befed by mixing at least two of these in line L44 before introducing tothe first reaction step or by directly introducing into a reactorwithout line L44. When employing mixing in line L44, line L44 may beheated for promoting a reaction in the line.

In the first reaction step, 2-(methylamino) ethanol andN-methyldiethanolamine are prepared by conducting the reaction at 50° C.or higher. A temperature of lower than 50° C. is disadvantageous becauseof tendency to reduction in a production efficiency for2-(methylamino)ethanol.

A pressure in the first reaction step depends on factors such as atemperature and starting materials; preferably 0.4 MPa or more. Apressure of less than 0.4 MPa may be disadvantageous because of tendencyto reduction in a consumption rate for ethylene oxide.

A reaction mixture containing 2-(methylamino)ethanol andN-methyldiethanolamine prepared in the first reaction step and unreactedmonomethylamine can be directly fed via lines L45, L47 and L49 to thesecond reaction step. The reaction mixture can be fed to the secondreaction step after being fed to line L5 and being premixed with othermaterials such as monomethylamine, carbon dioxide, the carbon dioxidecompound of monomethylamine, 1,3-dimethylurea and/or water supplied viaL2, and so on.

In the process of this invention, the amount of the second componentsupplied to the first reaction step is determined such that the totalmolar amount of the following i″) to iii″) is preferably at least threefolds, more preferably 3 to 40 folds both inclusive of the molar amountof ethylene oxide supplied. This molar ratio of less than 3 folds may bedisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while that of more than 40 folds may bedisadvantageous because of reduction in a volumetric efficiency of areactor, and increase in a cost for recovery of the unreactedmonomethylamine and the carbon dioxide compound of monomethylamine:

-   -   i″) the total of the molar amount of monomethylamine recovered        and recycled and the molar amount of monomethylamine newly        supplied;    -   ii″) the total of the molar amount of monomethylamine part in        the carbon dioxide compound of monomethylamine recovered and        recycled and the molar amount of monomethylamine newly supplied        in the carbon dioxide compound of monomethylamine; and    -   iii″) the total of the double of the molar amount of        1,3-dimethylurea recovered and recycled and the double of the        molar amount of 1,3-dimethylurea newly supplied.

Carbon dioxide used in the first reaction step may be used as gaseous,liquid, solid or supercritical carbon dioxide. The amount of the secondcomponent supplied to the first reaction step is determined such thatthe total molar amount of the following iv″) to vi″) is preferably 100folds or less of the molar amount of ethylene oxide supplied. This molarratio of more than 100 folds may be disadvantageous because of tendencyto reduction in a volumetric efficiency of the reactor:

-   -   iv″) the total of the molar amount of carbon dioxide part in the        carbon dioxide-compound of monomethylamine recovered and        recycled and the molar amount of carbon dioxide part in the        carbon dioxide compound of monomethylamine newly supplied;    -   v″) the total of the molar amount of carbon dioxide recovered        and recycled and the molar amount of carbon dioxide newly        supplied; and    -   vi″) the total of the molar amount of 1,3-dimethylurea recovered        and recycled and the molar amount of 1,3-dimethylurea newly        supplied.

In the first reaction step, the reaction may be conducted in thepresence of water, which is introduced via line L42. The amount of watersupplied is preferably 100 parts by weight or less, more preferably 50parts by weight or less to one part by weight of ethylene oxidesupplied. The amount of more than 100 parts by weight is disadvantageousbecause of reduction in a volumetric efficiency.

The process of this invention may comprise a seventh separation step(8). In such a case, a part or all of the reaction mixture prepared inthe first reaction step may be fed to the seventh separation step vialines L45 and L46. In the seventh separation step, a first fractioncontaining unreacted monomethylamine as a main component and a secondfraction containing 2-(methylamino)ethanol and N-methyldiethanolamine asmain components are separated from the reaction mixture. The firstfraction may be circulated to the first reaction step via line L50. Thesecond fraction is fed to the second reaction step via lines L48 andL49. The second fraction may be fed to the second reaction step afterfeeding the fraction to line L5 and premixing it with other materialssuch as monomethylamine, carbon dioxide and/or water from, for example,line L2.

To the second reaction step can be fed the reaction mixture obtained inthe first reaction step via lines L47 and L49 and/or the second fractionin the seventh separation step via lines L48 and L49, to feed2-(methylamino)ethanol and N-methyldiethanolamine produced in the firstreaction step to the second reaction step. When feeding at least one ofunreacted components (D), (E) and (F) to the second reaction step, thesecond reaction step may be conducted as such. Further, to the secondreaction step may be supplied monomethylamine via line L2, carbondioxide via line L3, the carbon dioxide compound of monomethylamine vialine L52 and/or 1,3-dimethylurea via line L53. To the second reactionstep may be supplied the reaction mixture in the first reaction step,the second fraction in the seventh separation step, monomethylamine,carbon dioxide, the carbon dioxide compound of monomethylamine,1,3-dimethylurea and/or water after mixing at least two of them.

In the second reaction step, the reaction is conducted at 100° C. orhigher, preferably 100° C. to 300° C. both inclusive, preferably with aresidence time of 1 to 24 hours both inclusive. A reaction temperatureof less than 100° C. is disadvantageous because of tendency to reductionin a production efficiency for 1,3-dimethyl-2-imidazolidinone while atemperature of more than 300° C. is disadvantageous because of tendencyto reduction in an yield of 1,3-dimethyl-2-imidazolidinone. A residencetime of less than 1 hour is disadvantageous because of tendency toreduction in a production efficiency for 1,3-dimethyl-2-imidazolidinonewhile a residence time of more than 24 hour is disadvantageous becauseof tendency to reduction in a volumetric efficiency of a reactor. Apressure depends on factors such as a temperature and the amounts ofstarting materials; preferably 4 MPa to 30 MPa both inclusive. Apressure of less than 4 MPa is disadvantageous because of tendency toreduction in a production efficiency for 1,3-dimethyl-2-imidazolidinonewhile a pressure of more than 30 MPa is disadvantageous because ofincrease in a production cost of a reactor.

In the process of this invention, the amount of the second componentsupplied to the second reaction step is determined such that the totalmolar amount of the following i′″) to iii′″) is preferably at least twofolds of the molar amount of ethylene oxide supplied to the firstreaction step. More preferably, the amount of monomethylamine isdetermined such that the above molar ratio is 2 to 39 folds bothinclusive. The molar ratio of less than two folds may be disadvantageousbecause of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while that of more than 39 folds may bedisadvantageous because of reduction in a volumetric efficiency of areactor, and increase in a cost for recovering unreactedmonomethylamine, the carbon dioxide compound of monomethylamine and1,3-dimethylurea:

-   -   i′″) the total of the molar amount of monomethylamine fed from        the first reaction step to the second reaction step, the molar        amount of monomethylamine recovered and recycled and the molar        amount of monomethylamine newly supplied;    -   ii′″) the total of the molar amount of monomethylamine part in        the carbon dioxide compound of monomethylamine fed from the        first reaction step to the second reaction step, the molar        amount of monomethylamine part in the carbon dioxide compound of        monomethylamine recovered and recycled and the molar amount of        monomethylamine in the carbon dioxide compound of        monomethylamine newly supplied; and    -   iii′″) the total of the double of the molar amount of        1,3-dimethylurea fed from the first reaction step to the second        reaction step, the double of the molar amount of        1,3-dimethylurea recovered and recycled and the double of the        molar amount of 1,3-dimethylurea newly supplied.

In the process of this invention, carbon dioxide used in the secondreaction step may be used as gaseous, liquid, solid or supercriticalcarbon dioxide. The amount of the second component supplied to thesecond reaction step is determined such that the total molar amount ofthe following iv″′) to vi″′) is preferably at least 1.5 folds, morepreferably 4 to 100 folds both inclusive of the molar amount of ethyleneoxide supplied. This molar ratio of less than 1.5 folds isdisadvantageous because of tendency to reduction in an yield of1,3-dimethyl-2-imidazolidinone, while the molar ratio of more than 100folds may be disadvantageous because of tendency to reduction in avolumetric efficiency of the reactor:

-   -   iv″′) the total of the molar amount of carbon dioxide fed from        the first reaction step to the second reaction step, the molar        amount of carbon dioxide recovered and recycled and the molar        amount of carbon dioxide newly supplied;    -   v″′) the total of the molar amount of carbon dioxide part in the        carbon dioxide compound of monomethylamine fed from the first        reaction step to the second reaction step, the molar amount of        carbon dioxide part in the carbon dioxide compound of        monomethylamine recovered and recycled and the molar amount of        carbon dioxide part in the carbon dioxide compound of        monomethylamine newly supplied; and    -   vi″′) the total of the molar amount of 1,3-dimethylurea fed from        the first reaction step to the second reaction step, the molar        amount of 1,3-dimethylurea recovered and recycled and the molar        amount of 1,3-dimethylurea newly supplied.

In the second reaction step, water may be introduced via line L4. Theamount of water supplied is determined such that the total of water fedfrom the first reaction step, water recovered and recycled in the secondreaction step and water newly supplied is preferably 100 parts by weightor less, more preferably 50 parts by weight or less to one part byweight of ethylene oxide supplied to the first reaction step.

In the 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step, DMI is produced. The reaction mixture obtained in the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep contains water; low-boiling amines which are amines having aboiling point higher than that of water and lower than that of DMI suchas 2-(methylamino)ethanol, 1,3-dimethylpiperazine andN,N′-dimethylethylenediamine; high-boiling compounds which are compoundshaving a boiling point higher than that of DMI such as 1,3-dimethylurea,1-methyl-2-imidazolidinone and N-methyldiethanolamine; ammonia and itscarbon dioxide compounds, monomethylamine, dimethylamine,trimethylamine, and carbon dioxide compounds of these amines; and carbondioxide, as byproducts or unreacted materials. Examples of a carbondioxide compound of ammonia or an amine include carbamates, carbonatesand hydrogencarbonates.

The reaction mixture in the 1,3-dimethyl-2-imidazolidinone preparationstep or the second reaction step is fed to the first separation step (2)via line L6.

In the first separation step, the reaction mixture obtained in the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep is separated into the first fraction containing monomethylamine,carbon dioxide and the carbon dioxide compound of monomethylamine asmain components, and also containing water; and the second fractioncontaining DMI and the above high-boiling compounds as main components,and also containing water. The first fraction may be fed to the fourthseparation step (5) via lines L7, L14, L16 and L19, while the secondfraction may be fed to the second separation step (3) via lines L8, L10and L13.

Separation in the first separation step is preferably conducted at apressure lower than that in the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step. Such a lower pressure mayfacilitate vaporization of low-boiling components such asmonomethylamine and a part of water, which are fed to the fourthseparation step.

The process of this invention may comprise an absorption step (10)between the first separation step and the fourth separation step. Insuch a case, the first fraction in the first separation step is fed tothe absorption step via lines L7, L14 and L15.

In the absorption step, the first fraction in the first separation stepis contacted with and absorbed in a solvent fed via line L17. The firstfraction in the first separation step may be introduced to theabsorption step as, for example, a gas, a liquid, a solution such as anaqueous solution or any mixture of these. Any solvent can be used aslong as it is inert to reaction substrates in the1,3-dimethyl-2-imidazolidinone preparation step, the first reaction stepand the second reaction step. Examples of a solvent used generallyinclude water, hydrocarbons, ethers, amides and circular ureas. Amongthese, water and DMI are preferable and water is more preferable. Waterand DMI are preferable because they are a starting material or productin the 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step, eliminating an additional recovery step. These solventsmay be used alone or in combination of two or more. Depending on asolvent used, the absorption may be conducted in a multiphase (two ormore phase) system.

A part of carbon dioxide which is not absorbed in a solvent in theabsorption step may be discharged outside of the system via line L20.

The absorption solution in the absorption step is supplied to the fourthseparation step (5) via lines L18 and L19.

In the fourth separation step, ammonia, dimethylamine, trimethylamine,the carbon dioxide compound of ammonia, the carbon dioxide compound ofdimethylamine, and the carbon dioxide compound of trimethylamineproduced as byproducts in the 1,3-dimethyl-2-imidazolidinone preparationstep or the second reaction step are removed into line L22 as the firstfraction. Monomethylamine and its carbon dioxide compound are recoveredas the second fraction from the bottom of the separator. When using theabsorption step, a part of the solvent in the absorption step isrecovered as the second fraction. The second fraction is recycled to the1,3-dimethyl-2-imidazolidinone preparation step via lines L23 and L5, orto the first reaction step and/or the second reaction step. A part ofthe second fraction may be discarded while the remaining may be recycledto the 1,3-dimethyl-2-imidazolidinone preparation step or to the firstreaction step and/or the second reaction step. The first fraction may bediscarded or undergo a disproportionation reaction to providemonomethylamine and then recycled to the 1,3-dimethyl-2-imidazolidinonepreparation step or the first reaction step and/or the second reactionstep.

The fourth separation step is preferably conducted in the presence ofcarbon dioxide for improving a separation/recovery efficiency formonomethylamine and/or its carbon dioxide compound. Carbon dioxide maybe used as any of gaseous, liquid, solid or supercritical carbondioxide. Because, the reaction is conducted in the presence of carbondioxide in the 1,3-dimethyl-2-imidazolidinone preparation step or thesecond reaction step, the separation in the fourth separation step canbe conducted without feeding additional carbon dioxide. Alternatively,the first fraction in the first separation step or the absorptionsolution fed from the absorption step can be contacted with carbondioxide supplied from line L21.

The fourth separation step may be conducted as a multistage process orcombined with a distillation process. Such a multistage process orcombination with a distillation process may improve a recoveryefficiency for monomethylamine.

When the fourth separation step is conducted as a multistage process,the first fraction in the first separation step may be absorbed in waterbefore being fed to a subsequent stage.

The second fraction containing DMI and the above high-boiling compoundsas main components and also containing water in the first separationstep is generally fed to the second separation step (3) via lines L8,L10 and L13.

The process of this invention may comprise a hydrolysis step (9) betweenthe first separation step and the second separation step. In such acase, 1,3-dimethylurea can be hydrolyzed by feeding the second fractionin the first separation step to the hydrolysis step via lines L8 and L9,in which step the fraction is heated at 50° C. or higher. Thehydrolysis-reaction mixture is separated into a first fractioncontaining, as main components, monomethylamine, carbon dioxide, and thecarbon dioxide compound of monomethylamine prepared by hydrolysis andalso containing water; and a second fraction containing DMI and theabove high-boiling compounds as main components and also containingwater. The first fraction is fed to the fourth separation step via linesL11, L14, L16 and L19. When using an absorption step, the first fractionis fed to the absorption step via lines L11, L14 and L15. The secondfraction is fed to the second separation step via lines L12 and L13.

The mixture containing water and DMI fed to the second separation stepvia line L13 is separated into the first fraction containing water andlow-boiling amines as main components and the second fraction containingDMI and the above high-boiling compounds as main components. The secondfraction is fed to the third separation step (4) via line L24. The firstfraction may be discarded, or recycled to the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep via lines L25, L26, L30 and L5, when the content of2-(methylamino)ethanol is low. When the content of2-(methylamino)ethanol is significant, at least part of the firstfraction may be recycled to the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step via lines L25, L26, L30 andL5. Alternatively, the fifth separation step (11) may be added forheighten the content of 2-(methylamino)ethanol in the circulatingliquid.

To the fifth separation step is fed the first fraction in the secondseparation step via lines L25 and L27. The fifth separation stepseparates the fraction into the first fraction containing water as amain component and the second fraction containing 2-(methylamino)ethanolas a main component. The second fraction is recycled to the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep via lines L29, L30 and L5. In the fifth separation step,2-(methylamino)ethanol may be separated for effectively recycling2-(methylamino) ethanol contained in the first fraction in the secondseparation step to the 1,3-dimethyl-2-imidazolidinone preparation stepor the second reaction step. The first fraction in the fifth separationstep may be discarded, or at least part of the fraction may be recycledto the 1,3-dimethyl-2-imidazolidinone preparation step or the secondreaction step.

The mixture containing DMI and the above high-boiling compounds fed tothe third separation step (4) via line L24 is separated into a firstfraction containing DMI as a main component and a second fractioncontaining the above high-boiling compounds as main components in thethird separation step.

DMI as a desired product is obtained as the first fraction in the thirdseparation step. A rectification step (12) may be added for providingDMI with a further improved purity. In such a case, the first fractionin the third separation step is fed to the rectification step via lineL32 and rectified in the rectification step to provide DMI with a highpurity.

At least part of the second fraction in the third separation step may berecycled to the 1,3-dimethyl-2-imidazolidinone preparation step or thesecond reaction step via lines L31, L33, L34 and L5. Circulation of thesecond fraction allows unreacted N-methyldiethanolamine to be recycled.Furthermore, 1,3-dimethylurea as a byproduct in the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep may be circulated to allow 1,3-dimethylurea to be reacted withwater in the reaction system and decomposed into monomethylamine, carbondioxide and the carbon dioxide compound of monomethylamine. It can,therefore, reduce the amounts of monomethylamine and carbon dioxidenewly supplied to the 1,3-dimethyl-2-imidazolidinone preparation step orthe second reaction step.

The process of this invention may comprise the sixth separation step(13) In such a case, the second fraction in the third separation step isfed to the sixth separation step via lines L31 and L37. In the sixthseparation step, the fraction is separated into a first fractioncontaining N-methyldiethanolamine and 1,3-dimethylurea as maincomponents and a second fraction containing compounds with a higherboiling point than that of 1,3-dimethylurea such as1-methyl-2-imidazolidinone as main components. At least part of thefirst fraction may be circulated into the 1,3-dimethyl-2-imidazolidinonepreparation step or the second reaction step via lines L39, L34 and L5.The second fraction may be discarded. Alternatively, this fraction mayundergo methylation to provide DMI and then fed to the third separationstep. The sixth separation step can allow N-methyldiethanolamine and/or1,3-dimethylurea to be effectively circulated into the1,3-dimethyl-2-imidazolidinone preparation step or the second reactionstep.

In the process of this invention, a reactor for the1,3-dimethyl-2-imidazolidinone preparation step, the first reaction stepand the second reaction step may be made of an appropriate knownmaterial, and a reactor whose inner wall is at least partly made of ametal and/or its oxide containing at least one selected from the groupconsisting of titanium and zirconium is preferable. Using such a reactormay allow DMIs to be prepared with a higher yield. Examples of such areactor include those totally made of a metal containing titanium orzirconium; and those whose inner wall is at least partly coated with ametal or its oxide containing titanium or zirconium. Examples of a metalcontaining titanium or zirconium include industrial pure titanium in JISGroups 1 to 4; anticorrosion titanium alloys such as Ti-0.15Pd, Ti-5Taand Ti-0.3Mo-0.8Ni; α-type titanium alloys such as Ti-2.5Sn,Ti-5Al-2.5Sn, Ti-5Al-2.5Sn(ELI), Ti-2.5Cu, Ti-20-1N-5Fe, Ti-5Ni-0.5Ru,Ti-0.5Pd-3Co and Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si; near α-typetitanium alloys such as Ti-8Al-1Mo-1V, Ti-2.25Al-11Sn-5Zr-1Mo-0.2Si,Ti-6Al-2Sn-4Zr-2Mo, Ti-5Al-5Sn-2Zr-2Mo-0.25Sn, Ti-6Al-2Nb-1Ta-0.8Mo,Ti-6Al-5Zr-0.5Mo-0.2Si and Ti-4.5Al-3V-2Fe-2Mo; α+β-type titanium alloyssuch as Ti-5Al-2Cr-1Fe, Ti-5Al-5Sn-5Zr-2Cr-1Fe, Ti-4Al-4Mn, Ti-3Al-2.5V,Ti-6Al-4V, Ti-6Al-4V(ELI), Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-6Mo,Ti-7Al-4Mo, Ti-5Al-2Zr-4Mo-4Cr, Ti-6Al-1.7Fe-0.1Si, Ti-6.4Al-1.2Fe,Ti-15Zr-4Nb-2Ta-2Pd, Ti-6Al-7Nb and Ti-8Mn; β-type titanium alloys suchas Ti-13V-11Cr-3Al, Ti-15Mo-5Zr, Ti-15Mo-0.2Pd, Ti-15V-3Cr-3Sn-3Al,Ti-20V-4Al-1Sn, Ti-22V-4Al and Ti-16V-4Sn-3Al-3Nb; near β-type titaniumalloys such as Ti-10V-2Fe-3Al and Ti-9.5V-2.5Mo-3Al; zirconium alloyssuch as zircaloy-2, zircaloy-4, Zr-2.5Nb and ozenite. Among thesemetals, titanium-containing metals are preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

In the process of this invention, a separator in the first separationstep may be made of an appropriate known material. In a preferableseparator, the inner wall is at least partly made of (I) a metal and/orits oxide containing at least one selected from the group consisting oftitanium and zirconium or (II) an inorganic glass. Use of such aseparator is advantageous because it may prevent solid formation andline clogging. Examples of a separator include those entirely made of ametal containing titanium or zirconium; those whose inner wall is atleast partially coated with a metal containing titanium or zirconium orits oxide; those entirely made of an inorganic glass; and those whoseinner wall is coated with an inorganic glass.

Examples of a metal containing titanium or zirconium may be as describedin the 1,3-dimethyl-2-imidazolidinone preparation step. Among thesemetals, a titanium-containing metal is preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

An inorganic glass in this invention means an inorganic material in aglass state, including element glasses, hydrogen-bonding glasses, oxideglasses, fluoride glasses, chloride glasses, sulfide glasses, carbonateglasses, nitrate glasses and sulfate glasses.

Among these, preferable glasses are oxide glasses such as silicateglasses, phosphate glasses and borate glasses. More preferable glassesare silicate glasses such as quartz glass; alkali-silicate glasses suchas water glass; soda-lime glasses such as sheet glass and crown glass;potash-lime glasses such as Bohemian glass and crystal glass; leadglasses such as flint glass; barium glasses such as barium flint glass;and silicate glasses such as borosilicate glass. Further preferableglasses include silicate glass, soda-lime glass and soda-lime glasscontaining aluminum, magnesium or calcium ions as modification ions.

In the process of this invention, a hydrolysis reactor in the hydrolysisstep may be made of an appropriate known material. Preferably is used ahydrolysis reactor, whose inner wall is at least partly made of (I) ametal and/or its oxide containing at least one selected from the groupconsisting of titanium and zirconium or (II) an inorganic glass. Use ofsuch a hydrolysis reactor is advantageous because it may prevent solidformation and line clogging. Examples of such a hydrolysis reactorinclude those entirely made of a metal containing titanium or zirconium;those whose inner wall is at least partially coated with a metalcontaining titanium or zirconium or its oxide; those entirely made of aninorganic glass; and those whose inner wall is coated with an inorganicglass.

Examples of a metal containing titanium or zirconium may be as describedin the 1,3-dimethyl-2-imidazolidinone preparation step. Among thesemetals, a titanium-containing metal is preferable and industrial puretitanium or an anticorrosion titanium alloy is more preferable.

Inorganic glasses which may be used are as described for the separator.Among these, preferable glasses are oxide glasses such as silicateglasses, phosphate glasses and borate glasses. More preferable glassesare silicate glasses such as quartz glass; alkali-silicate glasses suchas water glass; soda-lime glasses such as sheet glass and crown glass;potash-lime glasses such as Bohemian glass and crystal glass; leadglasses such as flint glass; barium glasses such as barium flint glass;and silicate glasses such as borosilicate glass. Further preferableglasses include silicate glass, soda-lime glass and soda-lime glasscontaining aluminum, magnesium or calcium ions as modification ions.

A style of a unit operation such as a reaction and separation in theprocess of this invention may be, but not limited to, a batch,semi-batch or continuous system.

The process of this invention allows byproducts to be effectivelyprocessed and DMI to be prepared with a higher efficiency.

This invention will be specifically described with reference to, but notlimited to, examples. In the following examples, a fraction in aseparation step or an absorption liquid in an absorption step areindicated, for instance, as follows: “the first fraction/the firstseparation step”, “the second fraction/the first separation step”, and“the absorption liquid/the absorption step.”

EXAMPLE 1

In an autoclave with an inner volume of 400 cc whose lid, stirring rodand stirring blade were made of industrial pure titanium of JIS Group 2and whose body was lined with industrial pure titanium of JIS Group 2were charged 111.4 g of methylamine methylcarbamate (1050 mmol), 32.4 gof ion-exchange water (1800 mmol). The gases phase was replaced withnitrogen and then 13.2 g of ethylene oxide (300 mmol) and 33.0 g ofcarbon dioxide (750 mmol) were charged. The autoclave was externallyheated with stirring for reacting the mixture at an internal temperatureof 100° C. for 3 hours. Then, the internal temperature was raised to200° C. and the mixture was reacted at the same temperature for 7 hours,during which the maximum pressure was 9.2 MPa.

After cooling the autoclave to an ambient temperature, the reactionmixture was opened to the atmospheric pressure. The reaction mixture wascollected for analyzing by gas chromatography. An yield of DMI based onethylene oxide was 46%.

EXAMPLE 2

[1,3-dimethyl-2-imidazolidinone Preparation Step (1st Time)]

In the autoclave described in Example 1 were charged the materials asdescribed in Example 1. The autoclave was externally heated withstirring and the mixture was reacted at an internal temperature of 220°C. for 4 hours, during which the pressure was 11.0 MPa.

The autoclave was cooled to an ambient temperature and opened to theatmospheric pressure to give 158.3 of the reaction mixture.

The collected reaction mixture was analyzed by gas chromatography andKarl Fischer method. An yield of DMI based on ethylene oxide was 57%.The reaction mixture contained 0.44 g of ammonia and ammonia part in itscarbon dioxide compound (hereinafter, collectively referred to as“ammonia component”); 36.8 g of monomethylamine and monomethylamine partin its carbon dioxide compound (hereinafter, collectively referred to as“monomethylamine component”); 1.12 g of dimethylamine and dimethylaminepart of its carbon dioxide compound (hereinafter, collectively referredto as “dimethylamine component”); 0.11 g of trimethylamine andtrimethylamine part in its carbon dioxide compound (hereinafter,collectively referred to as “trimethylamine component”); 19.4 g of1,3-dimethyl-2-imidazolidinone; 0.20 g of 2-(methylamino)ethanol and2-(methylamino)ethanol part in its carbon dioxide compound (hereinafter,collectively referred to as “2-(methylamino)ethanol component”); 0.41 gof 1,3-dimethylpiperazine; 0.20 g of N,N′-dimethylethylenediamine andN,N′-dimethylethylenediamine part in its carbon dioxide compound(hereinafter, collectively referred to as “N,N′-dimethylethylenediaminecomponent”); 0.44 g of N,N-dimethylethanolamine; 1.05 g of1-methyl-2-imidazolidinone; 2.57 g of N-methyldiethanolamine; 22.5 g of1,3-dimethylurea; 43.9 g of water; and 27.4 g of carbon dioxide, carbondioxide part of carbon dioxide compound of ammonia and carbon dioxidepart of carbon dioxide compound of the above amines (monomethylamine,dimethylamine, trimethylamine, 2-(methylamino)ethanol andN,N′-dimethylethylenediamine) (hereinafter, collectively referred to as“carbon dioxide component”).

Comparative Example 1

In the autoclave described in Example 1 were charged 88.6 g ofmethylamine methylcarbamate (835 mmol) and 52.2 g of ion-exchange water(2896 mmol). After the gaseous phase was replaced with nitrogen, 26.4 gof ethylene oxide (600 mmol) and 2.2 g of carbon dioxide (52 mmol). Theautoclave was externally heated with stirring and the mixture wasreacted at an internal temperature of 100° C. for 3 hours. The mixturewas further heated to an internal temperature of 220° C., and reacted atthe same temperature for 4 hours, during which the pressure was 3.3 MPa.The reaction mixture was collected and analyzed by gas chromatography asdescribed in Example 1. An yield of DMI based on ethylene oxide was 16%.

EXAMPLE 3

[The First Separation Step]

To a three-necked borosilicate glass flask with an inner volume of 500cc was placed 157.5 g of the reaction mixture collected in the1,3-dimethyl-2-imidazolidinone preparation step (1st time) in Example 2.Under an atmospheric pressure, it was purified by simple distillation atan internal temperature of 80 to 117° C. to obtain 73.0 g of a fraction(the first fraction/the first separation step) from a distillationcolumn. The first fraction/the first separation step was analyzed by gaschromatography and Karl Fischer method. The mixture contained 0.42 g ofthe ammonia component, 34.9 g of the monomethylamine component, 1.1 g ofthe dimethylamine component, 0.05 g of the trimethylamine component,18.6 g of the carbon dioxide component and 17.6 g of water.

The residue after simple distillation (the second fraction/the firstseparation step) was analyzed by gas chromatography and Karl Fischermethod. The residue contained 18.8 g of 1,3-dimethyl-2-imidazolidinone,22.0 g of 1,3-dimethylurea, 25.3 g of water, 0.20 g of2-(methylamino)ethanol and 1.03 g of 1-methyl-2-imidazolidinone.

[The Second Separation Step]

The second fraction/the first separation step was distilled under areduced pressure at 64 to 66° C./230 torr (31 kPa) to collect 27.0 g ofa fraction containing water (the first fraction/the second separationstep). The fraction was analyzed by gas chromatography and contained0.27 g of 1,3-dimethylpiperazine, 0.19 g ofN,N′-dimethylethylenediamine, 0.38 g of N,N-dimethylaminoethanol and0.19 g of 2-(methylamino)ethanol. The residue (the second fraction/thesecond separation step) was 43.8 g, containing 18.3 g of1,3-dimethyl-2-imidazolidinone, 21.5 g of 1,3-dimethylurea and 2.5 g ofN-methyldiethanolamine.

[The Third Separation Step]

The residue collected from the flask in the second separation step (thesecond fraction/the second separation step) was distilled under apressure at 105 to 109° C./19.5 torr (2.5 kPa) to collect 16.8 g of afraction containing 1,3-dimethyl-2-imidazolidinone with a purity of 99%.

[The Fourth Separation Step (Stage 1)]

The fraction collected in the first separation step (the firstfraction/the first separation step) was placed in a three-necked flaskwith an inner volume of 200 mL. The flask was externally cooled by icewhile 30 g of dry ice was slowly added until the system was saturatedwith carbon dioxide. Then, the top of the three-necked flask wasequipped with a condenser and a trap via glass tubes, and the trap wascooled by ice-water.

The three-necked flask was immersed in an oil bath at 120° C. Themixture was refluxed by heating for 1 hour during which the maximuminternal temperature of the flask was 93° C. After cooling to roomtemperature, 52.1 g of an aqueous solution in the flask (the secondfraction/the fourth separation step (stage 1)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 26.3 g of the monomethylamine component, 0.0082 g of theammonia component, 0.25 g of the dimethylamine component, 13.9 g of thecarbon dioxide component and 11.3 g of water without a detectable levelof the trimethylamine component.

[The Fourth Separation Step (Stage 2)]

In a 50 mL three-necked flask was placed the first fraction/the fourthseparation step (stage 1) collected in the trap containing 7.8 g of themonomethylamine component, 0.39 g of the ammonia component, 0.76 g ofthe dimethylamine component and 0.005 g of the trimethylamine component.While externally cooling the flask with ice, 20 g of dry ice was slowlyadded until the system was saturated with carbon dioxide. Then, themixture was refluxed by heating for 1 hour using the apparatus asdescribed for the fourth separation step (stage 1), during which themaximum internal temperature in the flask was 93° C. After cooling toroom temperature, 13.7 g of a solution in the flask (the secondfraction/the fourth separation step (stage 2)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 6.1 g of the monomethylamine component, 0.0058 g of theammonia component, 0.19 g of the dimethylamine component, 3.3 g of thecarbon dioxide component and 4.1 g of water without a detectable levelof the trimethylamine component.

[1,3-dimethyl-2-imidazolidinone Preparation Step (2nd Time)]

In the autoclave as described in the 1,3-dimethyl-2-imidazolidinonepreparation step (1st time) was charged 63.8 g of the aqueous solution(31.5 g of the monomethylamine component, 16.7 g of the carbon dioxidecomponent and 14.8 g of water) containing monomethylamine (the secondfraction/the fourth separation step (stage 1) and, the secondfraction/the fourth separation step (stage 2)) collected in the fourthseparation step (stage 1) and the fourth separation step (stage 2)respectively, and then charged 17.6 g of ion-exchange water and 57.6 gof methylamine methylcarbamate. After replacing the gaseous phase withnitrogen, 13.2 g of ethylene oxide (300 mmol) and 38.7 g of carbondioxide were charged. That is, the materials were charged such that thetotal of the molar amount of monomethylamine and the molar amount of themonomethylamine part in the carbon dioxide compound of monomethylamine,the total of the molar amount of carbon dioxide and the molar amount ofthe carbon dioxide part in the carbon dioxide compound ofmonomethylamine, and the molar amount of water was equal to thosecharged in the 1,3-dimethyl-2-imidazolidinone preparation step (1sttime) respectively. The mixture was reacted at an internal temperatureof 220° C. for 4 hours as described for the1,3-dimethyl-2-imidazolidinone preparation step (1st time).

The reaction mixture was collected and analyzed as described for the1,3-dimethyl-2-imidazolidinone preparation step (1st time). An yield ofDMI based on ethylene oxide was 56%. The reaction mixture contained 1.1g of 1-methyl-2-imidazolidinone and 0.45 g of the ammonia component.

Comparative Example 2

In the 1,3-dimethyl-2-imidazolidinone preparation step (2nd time) inExample 3, 72.0 g of the first fraction/the first separation step (34.4g of the monomethylamine component, 0.41 g of the ammonia component,1.05 g of the dimethylamine component, 18.3 g of the carbon dioxidecomponent and 17.4 g of water) was charged in place of the secondfraction/the fourth separation step (stage 1) and the secondfraction/the fourth separation step (stage 2). Furthermore, materialswere charged so that the amounts of monomethylamine component, thecarbon dioxide component, water and ethylene oxide were equal to thosecharged in the 1,3-dimethyl-2-imidazolidinone preparation step (2ndtime) in Example 3. Reaction and analysis were conducted as describedfor the 1,3-dimethyl-2-imidazolidinone preparation step (2nd time) inExample 3. An yield of DMI based on ethylene oxide was 50%. The reactionmixture contained 2.1 g of 1-methyl-2-imidazolidinone and 0.86 g of theammonia component.

As described above, monomethylamine collected in the fourth separationstep may be circulated for recycling to prevent increase of byproductsand provide DMI with a higher yield.

EXAMPLE 4

[The First Reaction Step (1st Time)]

In the autoclave as described in Example 1 was charged 37.8 g ofion-exchange water (2100 mmol). After replacing the gaseous phase withnitrogen, 93.2 g of monomethylamine (3000 mmol) and 23.8 g of carbondioxide (540 mmol) were charged. The autoclave was externally heated toan internal temperature of 100° C. with stirring. After the internaltemperature reached 100° C., 13.2 g of ethylene oxide (300 mmol) wasadded, and the mixture was heated at an internal temperature of 100° C.for 1 hour.

[The Seventh Separation Step]

The autoclave in the first reaction step (1st time) was cooled to 70°C., and was gradually opened to the atmospheric pressure whilemonomethylamine was collected from the gaseous phase into a pressurebottle with an inner volume of 200 cc cooled to −78° C. (the firstfraction/the seventh separation step) to provide 42.7 g ofmonomethylamine.

[The Second Reaction Step (1st Time)]

Gas chromatography for the residual reaction mixture in the autoclave inthe seventh separation step (the second fraction/the seventh separationstep) indicated that no ethylene oxide existed and that yields for2-(methylamino) ethanol and N-methyldiethanolamine based on ethyleneoxide were 85% and 15%, respectively. The reaction mixture contained19.2 of the 2-(methylamino)ethanol component, 2.68 g of theN-methyldiethanolamine component, 41.8 g of the monomethylaminecomponent, 37.8 g of water and 23.8 g of the carbon dioxide component.

Then, 16.4 g of ion-exchange water (913 mmol), 14.3 g of monomethylamine(461 mmol) and 55.6 g of carbon dioxide (1263 mmol) were charged in theautoclave containing the reaction mixture (the second fraction/theseventh separation step) comprising 19.0 g of the 2-(methylamino)ethanolcomponent, 2.67 g of the N-methyldiethanolamine, 41.6 g of themonomethylamine component, 23.6 g of the carbon dioxide component and37.6 g of water. The mixture was reacted at an internal temperature of200° C. for 5 hours, during which the maximum pressure was 8.3 MPa.

After cooling the autoclave to room temperature, it was opened to theatmospheric pressure to collect 176.2 g of the reaction mixture.

The reaction mixture was analyzed by gas chromatography and Karl Fischermethod, indicating that an yield for 1,3-dimethyl-2-imidazolidinone was76% based on ethylene oxide. The reaction mixture contained 0.35 g ofthe ammonia component, 32.1 g of the monomethylamine component, 0.88 gof the dimethylamine component, 0.11 g of the trimethylamine component,26.0 g of 1,3-dimethyl-2-imidazolidinone, 0.64 g of the2-(methylamino)ethanol component, 0.77 g of 1,3-dimethylpiperazine, 0.69g of the N,N′-dimethylethylenediamine component, 0.42 g ofN,N-dimethylethanolamine, 0.42 g of 1-methyl-2-imidazolidinone, 1.34 gof N-methyldiethanolamine, 20.3 g of 1,3-dimethylurea, 67.1 g of waterand 24.3 g of the carbon dioxide component.

[The First Separation Step and an Absorption Step]

In a borosilicate glass three-necked flask with an inner volume of 500cc was placed 174.4 g of the reaction mixture collected in the secondreaction step (1st time). The mixture was simply distilled under anambient pressure at an internal temperature of 80 to 117° C. while afraction from a distillation column was contacted with and absorbed in10 g of ion-exchange water in a flask with an inner volume of 200 cc toobtain 86.4 g of an aqueous solution containing the fraction. Theaqueous solution (absorption solution/absorption step) was analyzed bygas chromatography and Karl Fischer method. It contained 0.34 g of theammonia component, 31.5 g of the monomethylamine component, 0.86 g ofthe dimethylamine component, 0.11 g of the trimethylamine component,16.7 g of the carbon dioxide component and 36.9 g of water.

The residue after the simple distillation (the second fraction/the firstseparation step) was also analyzed by gas chromatography and KarlFischer method. The residue contained 25.2 g of1,3-dimethyl-2-imidazolidinone, 19.9 g of 1,3-dimethylurea, 38.8 g ofwater, 0.63 g of 2-(methylamino)ethanol and 0.42 g of1-methyl-2-imidazolidinone.

[The Second Separation Step]

The second fraction/the first separation step was distilled in vacuo at64 to 66° C./230 torr (31 kPa) to collect 40.5 g of a water-containingfraction (the first fraction/the second separation step). The fractionwas analyzed by gas chromatography, indicating that it contained 0.51 gof 1,3-dimethylpiperazine, 0.66 g of N,N′-dimethylethylenediamine, 0.36g of N,N-dimethylaminoethanol and 0.61 g of 2-(methylamino)ethanol. Thedistillation left 46.2 g of a residue (the second fraction/the secondseparation step) containing 24.5 g of 1,3-dimethyl-2-imidazolidinone,19.5 g of 1,3-dimethylurea and 1.3 g of N-methyldiethanolamine.

[The Third Separation Step]

The residue collected from the flask in the second separation step (thesecond fraction/the second separation step) was distilled in vacuo at105 to 109° C./19.5 torr (2.5 kPa) to collect 22.6 g of1,3-dimethyl-2-imidazolidinone with a purity of 99% as adistillate (thefirst fraction/the third separation step).

[The Fourth Separation Step (Stage 1)]

In a three-necked flask with an inner volume of 200 mL was placed theaqueous solution containing the fraction collected in the firstseparation step (absorption solution/absorption step). While externallycooling the flask with ice, 30 g of dry ice was slowly added until thesystem was saturated with carbon dioxide. Then, the top of thethree-necked flask was equipped with a trap containing 10 g ofion-exchange water via a glass tube, and the trap was cooled byice-water.

The three-necked flask was immersed in an oil bath at 120° C., and themixture was refluxed by heating for 1 hour during which the maximuminternal temperature of the flask was 93° C. After cooling to roomtemperature, 54.3 g of an aqueous solution in the flask (the secondfraction/the fourth separation step (stage 1)) was collected andanalyzed by gas chromatography and Karl Fischer method. The solutioncontained 23.7 g of the monomethylamine component, 0.0068 g of theammonia component, 0.20 g of the dimethylamine component, 12.5 g of thecarbon dioxide component and 17.3 g of water without a detectable levelof the trimethylamine component.

[The Fourth Separation Step (Stage 2)]

In a 200 mL three-necked flask was placed the aqueous solution of thefirst fraction/the fourth separation step (stage 1) collected in thetrap. This solution contained 7.1 g of the monomethylamine component,0.32 g of the ammonia component, 0.63 g of the dimethylamine componentand 0.072 g of the trimethylamine component. While externally coolingthe flask with ice, 20 g of dry ice was slowly added until the systemwas saturated with carbon dioxide. Then, the mixture was refluxed byheating for 1 hour using the apparatus as described for the fourthseparation step (stage 1), during which the maximum internal temperaturein the flask was 93° C. After cooling to room temperature, 21.8 g of asolution in the flask (the second fraction/the fourth separation step(stage 2)) was collected and analyzed by gas chromatography and KarlFischer method. The solution contained 5.6 g of the monomethylaminecomponent, 0.0049 g of the ammonia component, 0.16 g of thedimethylamine component, 3.0 g of the carbon dioxide component and 12.9g of water without a detectable level of the trimethylamine component.

An aqueous solution containing 74.0 g of monomethylamine (the secondfraction/the fourth separation step) was obtained as the total of thesecond fraction/the fourth separation step (stage 2) and the secondfraction/the fourth separation step (stage 1).

[The First Reaction Step (2nd time)]

In the autoclave as described in the first reaction step (1st time) wascharged 69.5 g of the aqueous solution containing monomethylamine (thesecond fraction/the fourth separation step) (26.9 g of themonomethylamine component, 14.2 g of the carbon dioxide component and27.5 g of water) collected in the fourth separation step (stage 1) andthe fourth separation step (stage 2), and then 10.3 g of ion-exchangewater. After replacing the gaseous phase with nitrogen, 42.5 g of thefirst fraction/the seventh separation step collected in the seventhseparation step, 23.8 g of monomethylamine and 9.5 g of carbon dioxidewere charged. That is, the materials were charged such that the total ofthe molar amount of monomethylamine and the molar amount of themonomethylamine part in the carbon dioxide compound of monomethylamine,the total of the molar amount of carbon dioxide and the molar amount ofthe carbon dioxide part in the carbon dioxide compound ofmonomethylamine, and the molar amount of water was equal to thosecharged in the first reaction step (1st time). With stirring, theautoclave was externally heated to an internal temperature of 100° C.After the internal temperature reached 100° C., 13.2 g of ethylene oxide(0.3 mol) was added and heating was continued at an internal temperatureof 100° C. for 1 hour.

The reaction mixture was collected and analyzed by gas chromatography asdescribed in the second reaction step (1st time), indicating that anconversion ratio of ethylene oxide was 100% and yields of2-(methylamino)ethanol and N-methyldiethanolamine were 85% and 15%,respectively, based on ethylene oxide newly charged in the firstreaction step (2nd time).

[The Second Reaction Step (2nd Time)]

To the reaction mixture left in the autoclave in the first reaction step(2nd time) containing 18.9 g of the 2-(methylamino)ethanol component,2.65 g of N-methyldiethanolamine, 41.7 g of the monomethylaminecomponent, 23.8 g of the carbon dioxide component and 37.8 g of waterwere added 4.5 g of the monomethylamine-containing aqueous solutioncomprising 1.76 g of the monomethylamine component, 0.93 g of the carbondioxide component and 1.80 g of water (the second fraction/the fourthseparation step) collected in the fourth separation step (stage 1) andthe fourth separation step (stage 2); 21.0 g of the residue containing17.8 g of 1,3-dimethylurea in the third separation step (the secondfraction/the third separation step); and then 18.3 g of ion-exchangewater. After replacing the gaseous phase with nitrogen, 45.8 g of carbondioxide was charged. That is, the following a) to c) were charged in anequal amount to that in the second reaction step (1st time),respectively:

-   -   a) the total of the molar amount of monomethylamine, the molar        amount of the monomethylamine part in the carbon dioxide        compound of monomethylamine and the double of the molar amount        of 1,3-dimethylurea,    -   b) the total of the molar amount of carbon dioxide, the molar        amount of the carbon dioxide part in the carbon dioxide compound        of monomethylamine, the molar amount of the carbon dioxide part        in the carbon dioxide compound of 2-(methylamino)ethanol and the        molar amount of 1,3-dimethylurea, and    -   c) a difference between the molar amount of water and the molar        amount of 1,3-dimethylurea.

The mixture was reacted at an internal temperature of 200° C. for 5hours as described in the second reaction step (1st time).

The reaction mixture was collected and analyzed as described in thesecond reaction step (1st time), indicating that an yield of1,3-dimethyl-2-imidazolidinone was 76% based on ethylene oxide newlycharged in the first reaction step (2nd time).

Industrial Applicability

As described above, the process of this invention is suitable forindustrially preparing a 1,3-dialkyl-2-imidazolidinones using anindustrially readily available alkylene oxide as a starting material. Inparticular, in a process for preparing 1,3-dimethyl-2-imidazolidinone,1,3-dimethyl-2-imidazolidinone can be prepared with a higher efficiencywhile effectively separating and processing byproducts such asN-methyldiethanolamine, ammonia, dimethylamine, trimethylamine,1-methyl-2-imidazolidinone and 1,3-dimethylurea.

1. A process for preparing a 1,3-dimethyl-2-imidazolidinone by usingethylene oxide as a first component, using at least one selected fromthe group consisting of the following components (D), (E) and (F) as asecond component: component (D): carbon dioxide and monomethylamine;component (E): a carbon dioxide compound of monomethylamine andcomponent (F): 1,3-dimethylurea, wherein the process comprises: (1) a1,3-dimethyl-2-imidazolidinone preparation step of preparing1,3-dimethyl-2-imidazolidinone by heating said first component and saidsecond component at 50° C. or higher, characterized in that the reactionis conducted under a pressure of 4 MPa or higher and that1,3-dimethyl-2-imidazolidinone is prepared via correspondingN-alkylmonoethanolamine and N-alkyldiethanolamine as intermediates, andthe total molar amount of a molar feed amount of the monomethylamineincluded in the component (D), a molar feed amount of themonomethylamine part of the carbon dioxide compound of monomethylamine,said compound being component (E), and the double of a molar feed amountof the 1,3-dimethylurea, said 1,3-dimethylurea being component (F), isat least three folds of a molar feed amount of said ethylene oxide andcharacterized in that the total molar amount of a molar feed amount ofthe carbon dioxide included in the component (D), a molar feed amount ofthe carbon dioxide part of the carbon dioxide compound ofmonomethylamine, said compound being the component (E), and a molar feedamount of the 1,3-dimethylurea, said 1,3-dialkylurea being the component(F), is at least one and a half folds of a molar feed amount of saidethylene oxide and the process further comprises: (2) a first separationstep of separating the reaction mixture obtained in the1,3-dimethyl-2-imidazolidinone preparation step into a first fractioncontaining monomethylamine, carbon dioxide and a carbon dioxide compoundof monomethylamine as main components, and also containing water; and asecond fraction containing 1,3-dimethyl-2-imidazolidinone andhigh-boiling compounds with a higher boiling point than that of1,3-dimethyl-2-imidazolidinone as main components, and also containingwater; (3) a second separation step of separating at least part of thesecond fraction in the first separation step into a first fractioncontaining water and low-boiling amines with a boiling point higher thanthat of water and lower than that of 1,3-dimethyl-2-imidazolidinone asmain components; and a second fraction containing1,3-dimethyl-2-imidazolidinone and said high-boiling compounds as maincomponents; (4) a third separation step of separating the secondfraction in the second separation step into a first fraction containing1,3-dimethyl-2-imidazolidinone as a main component; and a secondfraction containing said high-boiling compounds as main components; and(5) a fourth separation step of separating the first fraction in thefirst separation step into a first fraction containing ammonia,dimethylamine, trimethylamine, a carbon dioxide compound of ammonia, acarbon dioxide compound of dimethylamine and a carbon dioxide compoundof trimethylamine as main components, and also containing water; and asecond fraction containing monomethylamine and a carbon dioxide compoundof monomethylamine as main components, and also containing water, whereat least part of the second fraction in the fourth separation step issupplied in the 1,3-dimethyl-2-imidazolidinone preparation step.
 2. Theprocess as claimed in claim 1, characterized in that the1,3-dimethyl-2-imidazolidinone preparation step is carried out by: (6) afirst reaction step of heating ethylene oxide and at least one selectedfrom the group consisting of the components (D), (E) and (F) at 50° C.or higher to prepare N-methyldiethanolamine and 2-(methylamino)ethanol;and (7) a second reaction step of heating N-methyldiethanolamine and2-(methylamino)ethanol prepared in the first reaction step with at leastone selected from the group consisting of the components (D), (E) and(F) at 100° C. or higher to prepare 1,3-dimethyl-2-imidazolidinone, andthe second fraction in the fourth separation step is supplied in saidfirst reaction step and/or said second reaction step.
 3. The process asclaimed in claim 2, characterized in that in the fourth separation step,at least part of the first fraction in the first separation step iscontacted with carbon dioxide, heated at 50° C. or higher, and separatedby vapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.
 4. The process asclaimed in claim 1, characterized in that in the fourth separation step,at least part of the first fraction in the first separation step iscontacted with carbon dioxide, heated at 50° C. or higher, and separatedby vapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.
 5. A process forpreparing a 1,3-dimethyl-2-imidazolidinone by using ethylene oxide as afirst component, using at least one selected from the group consistingof the following components (D), (E) and (F) as a second component:component (D): carbon dioxide and monomethylamine; component (E): acarbon dioxide compound of monomethylamine and component (F):1,3-dimethylurea, wherein the process comprises: (1) a1,3-dimethyl-2-imidazolidinone preparation step of preparing1,3-dimethyl-2-imidazolidinone by heating said first component and saidsecond component at 50° C. or higher, characterized in that the1,3-dimethyl-2-imidazolidinone is prepared via correspondingN-alkylmonoethanolamine and N-alkyldiethanolamine as intermediates, andthe total molar amount of a molar feed amount of the monomethylamineincluded in the component (D), a molar feed amount of themonomethylamine part of the carbon dioxide compound of monomethylamine,said compound being component (E), and the double of a molar feed amountof the 1,3-dimethylurea, said 1,3-dimethylurea being component (F), isat least three folds of a molar feed amount of said ethylene oxide andcharacterized in that the total molar amount of a molar feed amount ofthe carbon dioxide included in the component (D), a molar feed amount ofthe carbon dioxide part of the carbon dioxide compound ofmonomethylamine, said compound being the component (E), and a molar feedamount of the 1,3-dimethylurea, said 1,3-dialkylurea being the component(F), is at least one and a half folds of a molar feed amount of saidethylene oxide and the process further comprises: (2) a first separationstep of separating the reaction mixture obtained in the1,3-dimethyl-2-imidazolidinone preparation step into a first fractioncontaining monomethylamine, carbon dioxide and a carbon dioxide compoundof monomethylamine as main components, and also containing water; and asecond fraction containing 1,3-dimethyl-2-imidazolidinone andhigh-boiling compounds with a higher boiling point than that of1,3-dimethyl-2-imidazolidinone as main components, and also containingwater; (3) a second separation step of separating at least part of thesecond fraction in the first separation step into a first fractioncontaining water and low-boiling amines with a boiling point higher thanthat of water and lower than that of 1,3-dimethyl-2-imidazolidinone asmain components; and a second fraction containing1,3-dimethyl-2-imidazolidinone and said high-boiling compounds as maincomponents; (4) a third separation step of separating the secondfraction in the second separation step into a first fraction containing1,3-dimethyl-2-imidazolidinone as a main component; and a secondfraction containing said high-boiling compounds as main components; and(5) a fourth separation step of separating the first fraction in thefirst separation step into a first fraction containing ammonia,dimethylamine, trimethylamine, a carbon dioxide compound of ammonia, acarbon dioxide compound of dimethylamine and a carbon dioxide compoundof trimethylamine as main components, and also containing water; and asecond fraction containing monomethylamine and a carbon dioxide compoundof monomethylamine as main components, and also containing water, whereat least part of the second fraction in the fourth separation step issupplied in the 1,3-dimethyl-2-imidazolidinone preparation step.
 6. Theprocess as claimed in claim 5, characterized in that the1,3-dimethyl-2-imidazolidinone preparation step is carried out by: (6) afirst reaction step of heating ethylene oxide and at least one selectedfrom the group consisting of the components (D), (E) and (F) at 50° C.or higher to prepare N-methyldiethanolamine and 2-(methylamino)ethanol;and (7) a second reaction step of heating N-methyldiethanolamine and2-(methylamino)ethanol prepared in the first reaction step with at leastone selected from the group consisting of the components (D), (E) and(F) at 100° C. or higher to prepare 1,3-dimethyl-2-imidazolidinone, andthe second fraction in the fourth separation step is supplied in saidfirst reaction step and/or said second reaction step.
 7. The process asclaimed in claim 6, characterized in that in the fourth separation step,at least part of the first fraction in the first separation step iscontacted with carbon dioxide, heated at 50° C. or higher, and separatedby vapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.
 8. The process asclaimed in claim 5, characterized in that in the fourth separation step,at least part of the first fraction in the first separation step iscontacted with carbon dioxide, heated at 50° C. or higher, and separatedby vapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.
 9. A process forpreparing a 1,3-dimethyl-2-imidazolidinone by using ethylene oxide as afirst component, using at least one selected from the group consistingof the following components (D), (E) and (F) as a second component:component (D): carbon dioxide and monomethylamine; component (E): acarbon dioxide compound of monomethylamine; and component (F):1,3-dimethylurea, wherein the process comprises: (1) a1,3-dimethyl-2-imidazolidinone preparation step of preparing1,3-dimethyl-2-imidazolidinone by heating said first component and saidsecond component at 50° C. or higher, characterized in that the reactionis conducted under a pressure of 4 MPa or higher and that1,3-dimethyl-2-imidazolidinone is prepared via correspondingN-alkylmonoethanolamine and N-alkyldiethanolamine as intermediates, andthe total molar amount of a molar feed amount of the monomethylamineincluded in the component (D), a molar feed amount of themonomethylamine part of the carbon dioxide compound of monomethylamine,said compound being component (E), and the double of a molar feed amountof the 1,3-dimethylurea, said 1,3-dimethylurea being component (F), isat least three folds of a molar feed amount of said ethylene oxide andthe process further comprises: (2) a first separation step of separatingthe reaction mixture obtained in the 1,3-dimethyl-2-imidazolidinonepreparation step into a first fraction containing monomethylamine,carbon dioxide and a carbon dioxide compound of monomethylamine as maincomponents, and also containing water; and a second fraction containing1,3-dimethyl-2-imidazolidinone and high-boiling compounds with a higherboiling point than that of 1,3-dimethyl-2-imidazolidinone as maincomponents, and also containing water; (3) a second separation step ofseparating at least part of the second fraction in the first separationstep into a first fraction containing water and low-boiling amines witha boiling point higher than that of water and lower than that of1,3-dimethyl-2-imidazolidinone as main components; and a second fractioncontaining 1,3-dimethyl-2-imidazolidinone and said high-boilingcompounds as main components; (4) a third separation step of separatingthe second fraction in the second separation step into a first fractioncontaining 1,3-dimethyl-2-imidazolidinone as a main component; and asecond fraction containing said high-boiling compounds as maincomponents; and (5) a fourth separation step of separating the firstfraction in the first separation step into a first fraction containingammonia, dimethylamine, trimethylamine, a carbon dioxide compound ofammonia, a carbon dioxide compound of dimethylamine and a carbon dioxidecompound of trimethylamine as main components, and also containingwater; and a second fraction containing monomethylamine and a carbondioxide compound of monomethylamine as main components, and alsocontaining water, where at least part of the second fraction in thefourth separation step is supplied in the 1,3-dimethyl-2-imidazolidinonepreparation step.
 10. The process as claimed in claim 9, characterizedin that the 1,3-dimethyl-2-imidazolidinone preparation step is carriedout by: (6) a first reaction step of heating ethylene oxide and at leastone selected from the group consisting of the components (D), (E) and(F) at 50° C. or higher to prepare N-methyldiethanolamine and2-(methylamino)ethanol; and (7) a second reaction step of heatingN-methyldiethanolamine and 2-(methylamino)ethanol prepared in the firstreaction step with at least one selected from the group consisting ofthe components (D), (E) and (F) at 100° C. or higher to prepare1,3-dimethyl-2-imidazolidinone, and the second fraction in the fourthseparation step is supplied in said first reaction step and/or saidsecond reaction step.
 11. The process as claimed in claim 10,characterized in that in the fourth separation step, at least part ofthe first fraction in the first separation step is contacted with carbondioxide, heated at 50° C. or higher, and separated by vapor-liquidseparation to remove the first fraction in the fourth separation stepinto the gaseous phase and obtain the second fraction in the fourthseparation step from the liquid phase.
 12. The process as claimed inclaim 9, characterized in that in the fourth separation step, at leastpart of the first fraction in the first separation step is contactedwith carbon dioxide, heated at 50° C. or higher, and separated byvapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.
 13. A process forpreparing a 1,3-dimethyl-2-imidazolidinone by using ethylene oxide as afirst component, using at least one selected from the group consistingof the following components (D), (E) and (F) as a second component:component (D): carbon dioxide and monomethylamine; component (E): acarbon dioxide compound of monomethylamine; and component (F):1,3-dimethylurea, wherein the process comprises: (1) a1,3-dimethyl-2-imidazolidinone preparation step of preparing1,3-dimethyl-2-imidazolidinone by heating said first component and saidsecond component at 50° C. or higher, characterized in that the1,3-dimethyl-2-imidazolidinone is prepared via correspondingN-alkylmonoethanolamine and N-alkyldiethanolamine as intermediates, andthe total molar amount of a molar feed amount of the monomethylamineincluded in the component (D), a molar feed amount of themonomethylamine part of the carbon dioxide compound of monomethylamine,said compound being component (E), and the double of a molar feed amountof the 1,3-dimethylurea, said 1,3-dimethylurea being component (F), isat least three folds of a molar feed amount of said ethylene oxide andthe process further comprises: (2) a first separation step of separatingthe reaction mixture obtained in the 1,3-dimethyl-2-imidazolidinonepreparation step into a first fraction containing monomethylamine,carbon dioxide and a carbon dioxide compound of monomethylamine as maincomponents, and also containing water; and a second fraction containing1,3-dimethyl-2-imidazolidinone and high-boiling compounds with a higherboiling point than that of 1,3-dimethyl-2-imidazolidinone as maincomponents, and also containing water; (3) a second separation step ofseparating at least part of the second fraction in the first separationstep into a first fraction containing water and low-boiling amines witha boiling point higher than that of water and lower than that of1,3-dimethyl-2-imidazolidinone as main components; and a second fractioncontaining 1,3-dimethyl-2-imidazolidinone and said high-boilingcompounds as main components; (4) a third separation step of separatingthe second fraction in the second separation step into a first fractioncontaining 1,3-dimethyl-2-imidazolidinone as a main component; and asecond fraction containing said high-boiling compounds as maincomponents; and (5) a fourth separation step of separating the firstfraction in the first separation step into a first fraction containingammonia, dimethylamine, trimethylamine, a carbon dioxide compound ofammonia, a carbon dioxide compound of dimethylamine and a carbon dioxidecompound of trimethylamine as main components, and also containingwater; and a second fraction containing monomethylamine and a carbondioxide compound of monomethylamine as main components, and alsocontaining water, where at least part of the second fraction in thefourth separation step is supplied in the 1,3-dimethyl-2-imidazolidinonepreparation step.
 14. The process as claimed in claim 13, characterizedin that the 1,3-dimethyl-2-imidazolidinone preparation step is carriedout by: (6) a first reaction step of heating ethylene oxide and at leastone selected from the group consisting of the components (D), (E) and(F) at 50° C. or higher to prepare N-methyldiethanolamine and2-(methylamino)ethanol; and (7) a second reaction step of heatingN-methyldiethanolamine and 2-(methylamino)ethanol prepared in the firstreaction step with at least one selected from the group consisting ofthe components (D), (E) and (F) at 100° C. or higher to prepare1,3-dimethyl-2-imidazolidinone, and the second fraction in the fourthseparation step is supplied in said first reaction step and/or saidsecond reaction step.
 15. The process as claimed in claim 14,characterized in that in the fourth separation step, at least part ofthe first fraction in the first separation step is contacted with carbondioxide, heated at 50° C. or higher, and separated by vapor-liquidseparation to remove the first fraction in the fourth separation stepinto the gaseous phase and obtain the second fraction in the fourthseparation step from the liquid phase.
 16. The process as claimed inclaim 13, characterized in that in the fourth separation step, at leastpart of the first fraction in the first separation step is contactedwith carbon dioxide, heated at 50° C. or higher, and separated byvapor-liquid separation to remove the first fraction in the fourthseparation step into the gaseous phase and obtain the second fraction inthe fourth separation step from the liquid phase.